Z And outburst

[Francois Teyssier]

The prototypical symbiotic star Z And has been detected in outburst

Daily coverage (low and high resolution) is recommanded

François Teyssier


From VSNET :


Z And in full outburst. See my recent visual estimates:

ANDZ 20180116.830 10.03 DPV
ANDZ 20180118.847 10.03 DPV
ANDZ 20180121.853 9.86 DPV
ANDZ 20180122.865 9.81 DPV
ANDZ 20180215.846 9.08 DPV

Clear Skies!
Pavol A. Dubovsky & Zennox 76/700 mm
Associação de Astrónomos Amadores da Madeira, Portugal
Vihorlat Observatory Humenné, Slovakia

[Francois Teyssier]

Clear sky

Echelle spectrum following VSNET Alert
In comparison to recent spectra obtained by Joan Guarro

Raman OVI has vanished

zand_20180217_782_Raman.png (49.27 KiB) Viewed 4841 times

As did [Fe VII] (at least in comparison to the continuum)

zand_20180217_782_FeVII.png (30.2 KiB) Viewed 4841 times

Expected behavior for a classical symbiotic outburst

[OIII] 5007, He I 5016 and Fe II (42) 5018

zand_20180217_782_OIIII.png (18.29 KiB) Viewed 4841 times

Further observations are welcome

[Francois Teyssier]

Message from Augustin Skopal:

Also our photometry shows an increse of the optical brightness by >~1 mag
from the end of 2017. Unfortunately, it is just before its season gap.
This outburst seems to be a stronger one, i.e. comparable with
thouse peaked in December 2000, July 2006 and December 2009.

Both low-resolution spectra measured from shortest wavelength as
possible, and the medium-resolution spectra (R ~ 9000 - 11000 or more)
are important to carry out. The former are needed for modelling
the SED and the latter mainly for studying evolution of the strongest
line profiles. The main aim is to indicate the presence or absence of
satellite emission components to H-alpha and H-beta lines as during
the major 2006 and 2009-10 outbursts (see Skopal et al, 2009, ApJ,
690,1222). These satellite components signal high-velocity collimated
mass outflow (jets) - very rare event in symbiotic stars. Outbursts
with jets constrain special conditions that allow us to understand better
the accretion process and the nature of the Z And-type outbursts.

Good luck in observing Z And for all enthusiasts!

[Francois Teyssier]

Observations during the outburst

He II line
From echelle spectra obtained by Joan Guarro, Tim Lester and François Teyssier

ZAnd.JPG (42.62 KiB) Viewed 4701 times

Significant broadening of the line and shift toward blue
Can be interpredted as the result of increasing wind from the hot component

François Teyssier

[Francois Teyssier]

Monitoring of the outburst, (good coverage despite declining altitude of the star)
Echelle spectra obtained by Joan Guarro, Tim Lester, François Teyssier
corrected for heliocentric velocity

[Fe VII] still weakening

zand_2018_fevii.png (52.27 KiB) Viewed 4630 times

Raman OVI totally disappeared at the begining of the outburst

zand_2018_ovi.png (97.44 KiB) Viewed 4630 times

Blue shift of He II

zand_2018_heii.png (39.73 KiB) Viewed 4630 times

zand_2018_oiii.png (60.42 KiB) Viewed 4630 times

No satellite lines (jet) in Balmer lines.

zand_2018_Hb.png (39.95 KiB) Viewed 4630 times

Unfortunatly, the star is lower and lower

François Teyssier

[Francois Teyssier]

New observation Z And in the morning sky

[Fe VII] reappears, while Raman OVI reamains undetectable.

EW from Echelle spectra (J. Guarro, T. Lester, F. Teyssier)

[David Boyd]

Low resolution spectrum of Z And. Confirms [Fe VII] present but Raman OVI absent.

[Christian Buil]

David, François, a very similar spectrum taken by using a UVEX2 spectrograph prototype (see http://www.spectro-aras.com/forum/viewtopic.php?f=8&t=2085) :





(the jump feature in the UV region is real)

Christian Buil

[Francois Teyssier]

C'est excellent
On voit bien le saut de Balmer en effet, très intéressant
En plus la résolution est à un bon niveau avec [OIII] 5007 bien séparé de Fe II et He I
Une calibration en flux absolu là-dessus et c'est parfait pour ce genre d'étoile
Bravo Christian !

François

[Peter Somogyi]

Congratulations Christian for the breakthrough!
By chance, I've also visited this object in the near-UV (12" Newton, LHires 2400/mm, 35 micron slit, R~5500 average) on the weekend:

(Flux calibrated with 2-stars method on 15 And (miles), using the wide slit.)
There is a real absorption (visible on all raw images) near to H8, going below continuum. However, I'm not sure whether if it's a P-cyg profile of H8, or just from a different feature (H9 is a bit unfocused, H7 is contaminated - they are not confirming it well).
The Si II annotation needs to be verified, VSpec shown match with 2 strongest out of the 3 lines, and saw these features on F type stars (in form of absorption) mentioned before.
- Peter
EDIT: uploaded the flux corrected spectrum